More and more people take exercises, e.g., running and playing ball games, so as to keep fit. Usually, at a low temperature, people will be dressed in thick sportswear, which causes that sweat generated by the people during the exercise will be prevented from being evaporated in time. In the case that people are dressed in thin sportswear, they will feel cold before the exercise or it is impossible to maintain their body temperatures after the exercise, so they will catch cold easily.